[net-next 07/13] igb: Refactor clean_rx_irq to reduce overhead and improve performance

Jeff Kirsher
2011-09-17T08:04:47Z

From: Alexander Duyck <alexander.h.duyck@intel.com>

This change is meant to be a general cleanup and performance improvement
for clean_rx_irq. The previous patch should have updated the allocation so
that the rings can be treated as read-only within the clean_rx_irq
function. In addition I am re-ordering the operations such that several
goals are accomplished including reducing the overhead for packet
accounting, reducing the number of items on the stack, and improving
overall performance.

Signed-off-by: Alexander Duyck <alexander.h.duyck@intel.com>
Tested-by: Aaron Brown <aaron.f.brown@intel.com>
Signed-off-by: Jeff Kirsher <jeffrey.t.kirsher@intel.com>
---
drivers/net/ethernet/intel/igb/igb_main.c | 96 ++++++++++++++---------------
1 files changed, 47 insertions(+), 49 deletions(-)

diff --git a/drivers/net/ethernet/intel/igb/igb_main.c b/drivers/net/ethernet/intel/igb/igb_main.c
index 9fa2ad0..dd85df0 100644
--- a/drivers/net/ethernet/intel/igb/igb_main.c
+++ b/drivers/net/ethernet/intel/igb/igb_main.c
@@ -138,7 +138,7 @@ static void igb_setup_dca(struct igb_adapter *);
#endif /* CONFIG_IGB_DCA */
static bool igb_clean_tx_irq(struct igb_q_vector *);
static int igb_poll(struct napi_struct *, int);
-static bool igb_clean_rx_irq_adv(struct igb_q_vector *, int *, int);
+static bool igb_clean_rx_irq_adv(struct igb_q_vector *, int);
static int igb_ioctl(struct net_device *, struct ifreq *, int cmd);
static void igb_tx_timeout(struct net_device *);
static void igb_reset_task(struct work_struct *);
@@ -5481,28 +5481,27 @@ static int igb_poll(struct napi_struct *napi, int budget)
struct igb_q_vector *q_vector = container_of(napi,
struct igb_q_vector,
napi);
- int tx_clean_complete = 1, work_done = 0;
+ bool clean_complete = true;

#ifdef CONFIG_IGB_DCA
if (q_vector->adapter->flags & IGB_FLAG_DCA_ENABLED)
igb_update_dca(q_vector);
#endif
if (q_vector->tx_ring)
- tx_clean_complete = igb_clean_tx_irq(q_vector);
+ clean_complete = !!igb_clean_tx_irq(q_vector);

if (q_vector->rx_ring)
- igb_clean_rx_irq_adv(q_vector, &work_done, budget);
+ clean_complete &= igb_clean_rx_irq_adv(q_vector, budget);

- if (!tx_clean_complete)
- work_done = budget;
+ /* If all work not completed, return budget and keep polling */
+ if (!clean_complete)
+ return budget;

/* If not enough Rx work done, exit the polling mode */
- if (work_done < budget) {
- napi_complete(napi);
- igb_ring_irq_enable(q_vector);
- }
+ napi_complete(napi);
+ igb_ring_irq_enable(q_vector);

- return work_done;
+ return 0;
}

/**
@@ -5751,37 +5750,26 @@ static inline u16 igb_get_hlen(union e1000_adv_rx_desc *rx_desc)
return hlen;
}

-static bool igb_clean_rx_irq_adv(struct igb_q_vector *q_vector,
- int *work_done, int budget)
+static bool igb_clean_rx_irq_adv(struct igb_q_vector *q_vector, int budget)
{
struct igb_ring *rx_ring = q_vector->rx_ring;
- struct net_device *netdev = rx_ring->netdev;
- struct device *dev = rx_ring->dev;
- union e1000_adv_rx_desc *rx_desc , *next_rxd;
- struct igb_buffer *buffer_info , *next_buffer;
- struct sk_buff *skb;
- bool cleaned = false;
- u16 cleaned_count = igb_desc_unused(rx_ring);
- int current_node = numa_node_id();
+ union e1000_adv_rx_desc *rx_desc;
+ const int current_node = numa_node_id();
unsigned int total_bytes = 0, total_packets = 0;
- unsigned int i;
u32 staterr;
- u16 length;
+ u16 cleaned_count = igb_desc_unused(rx_ring);
+ u16 i = rx_ring->next_to_clean;

- i = rx_ring->next_to_clean;
- buffer_info = &rx_ring->buffer_info[i];
rx_desc = E1000_RX_DESC_ADV(*rx_ring, i);
staterr = le32_to_cpu(rx_desc->wb.upper.status_error);

while (staterr & E1000_RXD_STAT_DD) {
- if (*work_done >= budget)
- break;
- (*work_done)++;
- rmb(); /* read descriptor and rx_buffer_info after status DD */
+ struct igb_buffer *buffer_info = &rx_ring->buffer_info[i];
+ struct sk_buff *skb = buffer_info->skb;
+ union e1000_adv_rx_desc *next_rxd;

- skb = buffer_info->skb;
- prefetch(skb->data - NET_IP_ALIGN);
buffer_info->skb = NULL;
+ prefetch(skb->data);

i++;
if (i == rx_ring->count)
@@ -5789,42 +5777,48 @@ static bool igb_clean_rx_irq_adv(struct igb_q_vector *q_vector,

next_rxd = E1000_RX_DESC_ADV(*rx_ring, i);
prefetch(next_rxd);
- next_buffer = &rx_ring->buffer_info[i];

- length = le16_to_cpu(rx_desc->wb.upper.length);
- cleaned = true;
- cleaned_count++;
+ /*
+ * This memory barrier is needed to keep us from reading
+ * any other fields out of the rx_desc until we know the
+ * RXD_STAT_DD bit is set
+ */
+ rmb();

- if (buffer_info->dma) {
- dma_unmap_single(dev, buffer_info->dma,
+ if (!skb_is_nonlinear(skb)) {
+ __skb_put(skb, igb_get_hlen(rx_desc));
+ dma_unmap_single(rx_ring->dev, buffer_info->dma,
IGB_RX_HDR_LEN,
DMA_FROM_DEVICE);
buffer_info->dma = 0;
- skb_put(skb, igb_get_hlen(rx_desc));
}

- if (length) {
- dma_unmap_page(dev, buffer_info->page_dma,
- PAGE_SIZE / 2, DMA_FROM_DEVICE);
- buffer_info->page_dma = 0;
+ if (rx_desc->wb.upper.length) {
+ u16 length = le16_to_cpu(rx_desc->wb.upper.length);

skb_fill_page_desc(skb, skb_shinfo(skb)->nr_frags,
buffer_info->page,
buffer_info->page_offset,
length);

+ skb->len += length;
+ skb->data_len += length;
+ skb->truesize += length;
+
if ((page_count(buffer_info->page) != 1) ||
(page_to_nid(buffer_info->page) != current_node))
buffer_info->page = NULL;
else
get_page(buffer_info->page);

- skb->len += length;
- skb->data_len += length;
- skb->truesize += length;
+ dma_unmap_page(rx_ring->dev, buffer_info->page_dma,
+ PAGE_SIZE / 2, DMA_FROM_DEVICE);
+ buffer_info->page_dma = 0;
}

if (!(staterr & E1000_RXD_STAT_EOP)) {
+ struct igb_buffer *next_buffer;
+ next_buffer = &rx_ring->buffer_info[i];
buffer_info->skb = next_buffer->skb;
buffer_info->dma = next_buffer->dma;
next_buffer->skb = skb;
@@ -5833,7 +5827,7 @@ static bool igb_clean_rx_irq_adv(struct igb_q_vector *q_vector,
}

if (staterr & E1000_RXDEXT_ERR_FRAME_ERR_MASK) {
- dev_kfree_skb_irq(skb);
+ dev_kfree_skb_any(skb);
goto next_desc;
}

@@ -5844,7 +5838,7 @@ static bool igb_clean_rx_irq_adv(struct igb_q_vector *q_vector,

igb_rx_checksum_adv(rx_ring, staterr, skb);

- skb->protocol = eth_type_trans(skb, netdev);
+ skb->protocol = eth_type_trans(skb, rx_ring->netdev);

if (staterr & E1000_RXD_STAT_VP) {
u16 vid = le16_to_cpu(rx_desc->wb.upper.vlan);
@@ -5853,7 +5847,12 @@ static bool igb_clean_rx_irq_adv(struct igb_q_vector *q_vector,
}
napi_gro_receive(&q_vector->napi, skb);

+ budget--;
next_desc:
+ if (!budget)
+ break;
+
+ cleaned_count++;
/* return some buffers to hardware, one at a time is too slow */
if (cleaned_count >= IGB_RX_BUFFER_WRITE) {
igb_alloc_rx_buffers_adv(rx_ring, cleaned_count);
@@ -5862,7 +5861,6 @@ next_desc:

/* use prefetched values */
rx_desc = next_rxd;
- buffer_info = next_buffer;
staterr = le32_to_cpu(rx_desc->wb.upper.status_error);
}

@@ -5877,7 +5875,7 @@ next_desc:
if (cleaned_count)
igb_alloc_rx_buffers_adv(rx_ring, cleaned_count);

- return cleaned;
+ return !!budget;
}

static bool igb_alloc_mapped_skb(struct igb_ring *rx_ring,
--
1.7.6